package demo1;

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 28779
 * Date: 2023-04-24
 * Time: 13:20
 */
public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');

        A.left = B;
        A.right = C;
        B.right = E;
        B.left = D;
        C.right = G;
        C.left = F;
        E.right = H;


        return A;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null) {
            return ;
        }
        System.out.print(root.val + " ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root == null) {
            return ;
        }
        inOrder(root.left);
        System.out.print(root.val + " ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null) {
            return ;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    public int size1(TreeNode root) {
        if(root == null) {
            return 0;
        }
        return size1(root.left) + size1(root.right) + 1;
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    public int size2(TreeNode root) {
        if(root == null) {
            return 0;
        }
        nodeSize ++;
        size2(root.left);
        size2(root.right);
        return nodeSize;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    public int getLeafNodeCount1(TreeNode root) {
        if(root == null) {
            return 0;
        }
        if(root.left == null && root.right == null) {
            leafSize ++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
        return leafSize;
    }

    /*
     获取叶子节点的个数：子问题
     */
    public int getLeafNodeCount2(TreeNode root) {
        if(root == null) {
            return 0;
        }
        if(root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.right) + getLeafNodeCount2(root.left);
    }

    /*
    获取第K层节点的个数
     */
    public int getKLevelNodeCount(TreeNode root, int k) {
        if(root == null) {
            return 0;
        }
        if(k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left, k - 1) + getKLevelNodeCount(root.right, k - 1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
    */
    public int getHeight(TreeNode root) {
        if(root == null) {
            return 0;
        }
        int l = getHeight(root.left);
        int r = getHeight(root.right);
        return Math.max(l, r) + 1;
    }


    // 检测值为value的元素是否存在
    public TreeNode find(TreeNode root, char val) {
        if(root == null) {
            return null;
        }
        if(root.val == val) {
            return root;
        }
        TreeNode l = find(root.right, val);
        TreeNode r =find(root.left, val);
        return l == null ? r : l;
    }

    //层序遍历
    public void levelOrder(TreeNode root) {
        if(root == null) {
            return ;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while( !queue.isEmpty() ) {
            TreeNode cur = queue.poll();
            System.out.print(cur.val + " ");
            if(cur.left != null) {
                queue.offer(cur.left);
            }
            if(cur.right != null) {
                queue.offer(cur.right);
            }
        }
        System.out.println();
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if (root == null) return false;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            if(cur != null) {
                queue.offer(cur.left);
                queue.offer(cur.right);
            } else {
                break;
            }
        }

        while(!queue.isEmpty()) {
            TreeNode cur = queue.peek();
            if(cur == null) {
                queue.poll();
            } else {
                return false;
            }
        }
        return true;
    }

    //前序遍历（无递归）
    public void prePrint(TreeNode root) {
        if(root == null) {
            return ;
        }
        TreeNode cur = root;
        Stack<TreeNode> stack = new Stack<>();
        while(cur != null || !stack.empty()) {
            while(cur != null) {
                stack.push(cur);
                System.out.print(cur.val + " ");
                cur = cur.left;
            }
            TreeNode top = stack.pop();
            cur = top.right;
        }
    }
    //中序遍历（无递归）
    public void inPrint(TreeNode root) {
        if(root == null) {
            return ;
        }
        TreeNode cur = root;
        Stack<TreeNode> stack = new Stack<>();
        while(cur != null || !stack.empty()) {
            while(cur != null) {
                stack.push(cur);
                cur = cur.left;
            }
            TreeNode top = stack.pop();
            System.out.print(top.val + " ");
            cur = top.right;
        }
    }
    //后序遍历（无递归）
    public void postPrint(TreeNode root) {
        if(root == null) {
            return ;
        }

        TreeNode cur = root;
        TreeNode prev = null;
        Stack<TreeNode> stack = new Stack<>();

        while(cur != null || !stack.empty()) {
            while(cur != null) {
                stack.push(cur);
                cur = cur.left;
            }

            TreeNode top = stack.peek();

            if(top.right == null || top.right == prev) {
                System.out.print(top.val + " ");
                prev = top;
                stack.pop();
            } else {
                cur = top.right;
            }
        }
    }
}